1. Field of the Invention
The present invention relates to a bright and dark field switching device and a microscope. More particularly, the invention relates to a bright and dark field switching device which is provided on an optical path of an illuminating optical system and can switch bright field illumination and dark field illumination, and a microscope which can switch bright field illumination and dark field illumination.
2. Description of the Related Art
In order to carry out observation through a microscope, bright field illumination is used for checking a comparatively rough portion of an object upon a workpiece, and dark field illumination is required for checking a comparatively fine portion of the object upon a workpiece, for example, a circuit pattern of an IC to determine the presence of a flaw.
Therefore, there has been known a microscope comprising a bright and dark field switching device capable of switching the bright field illumination and the dark field illumination.
The related art bright and dark field switching device has switched the bright field illumination and the dark field illumination by using a slide unit 100 shown in FIG. 9.
The slide unit 100 includes a rectangular body portion 101 and an operation knob 102. The body portion 101 has three kinds of filters, specifically, a filter 103 for bright field observation (which will hereinafter be referred to xe2x80x9cbright field filterxe2x80x9d), a glare-proof filter 104 and a filter 105 for dark field observation (which will hereinafter be referred to xe2x80x9cdark field filterxe2x80x9d) which are provided rectilinearly.
In use, the slide unit 100 is inserted in the illuminating optical path of the microscope and the amount of push-in (or pull-out) of the slide unit 100 is changed so as to selectively position, on the illuminating optical path, either of the bright field filter 103 and the dark field filter 105 which are provided on the slide unit 100. Thus, the observation is carried out. In this case, when switching from the dark field filter 105 to the bright field filter 103 is to be carried out, the countermeasures are taken such that dazzling is not caused even if the dark field observation is switched into the bright field observation. More specifically, the glare-proof filter 104 is provided in the middle between the bright filed filter 103 and the dark field filter 105.
With the above-mentioned related art structure, however, the amount of movement of the slide unit 100 is increased with the switching. When the amount of pull-out is the greatest, the filter 105 close to the operation knob 102 gets out of the microscope body. Consequently, a refuse or dust sticks to a filter surface.
If the slide unit 100 is to be pulled out most greatly such that the filter 105 does not get out of the microscope body, the size of the microscope body should be increased. For this reason, a cost is increased and operability is lacking.
For such a problem, it is also proposed that a unit having a bright field filter and a dark field filter and a unit having a glare-proof filter should be provided separately from each other and should be operated independently, respectively.
With such a structure, however, the two units should be operated in separate positions from each other. Therefore, an alternate holding operation is required so that the operability is more deteriorated.
In order to solve the problems, it is an object of the invention to provide a bright and dark field switching device and a microscope which can carry out switching into three states of the bright field illumination, the dark field illumination and the glare-proof illumination with a reduction in a size and high operability.
In order to achieve the object, the bright and dark field switching device and a microscope according to the invention employ the following structure.
A bright and dark field switching device for a microscope provided on an optical path of an illuminating optical system, according to the present invention, comprises:
a glare-proof optical part for limiting the amount of light illuminated form the illuminating optical system;
an optical part for dark field observation;
a guide mechanism for holding the glare-proof optical part and the optical part for dark field observation such that they can be moved to the optical path and can be returned from the optical path; and
a switching mechanism for moving the glare-proof optical part and the optical part for dark field observation to the optical path and returning them from the optical path, and for moving the glare-proof optical part together and positioning the glare-proof optical part on the optical path only when returning the optical part for dark field observation from the optical path,
wherein the glare-proof optical part and the optical part for dark field observation are provided on both sides with the optical path of the illuminating optical system interposed therebetween.
The optical part for dark field observation indicates a condenser lens for a dark field (will hereinafter be referred to xe2x80x9ccondenser lensxe2x80x9d), a filter for a dark field or a metallic shielding mask.
According to such a structure, the glare-proof optical part and the optical part for dark field observation are provided through the guide mechanism on both sides with the optical path of the illuminating optical system interposed therebetween such that they can be moved to the optical path and can be returned from the optical path. The movement and return are carried out by the switching mechanism. Therefore, a smaller amount of movement is enough as compared with the structure of a slide unit having three kinds of related art filters provided rectilinearly. Therefore, even if the size of the device itself is not increased, the filter does not get out of the body. Accordingly, a reduction in the size of the device can be maintained.
Moreover, the switching mechanism can move the glare-proof optical part and the optical part for dark field observation to the optical path and can return them from the optical path. Also the switching mechanism can move the glare-proof optical part together and can position the same on the optical path only when returning the optical part for dark field observation from the optical path. Therefore, also when the switching is to be carried out from the dark field observation to the bright field observation, the glare-proof optical part is once positioned on the optical path. Consequently, an observer is not dazzled. Accordingly, the observer does not need to keep his (or her) eyes off from an eyepiece when carrying out the switching from the dark field observation to the bright field observation. Therefore, it is possible to carry out the switching from the bright field illumination to the dark field illumination without damaging operability.
In the above-mentioned the bright and dark field switching device, it is preferable that the guide mechanism includes:
a first slider having the glare-proof optical part and disposed on a microscope body of the microscope movably in a direction parallel with movement and return of the glare-proof optical part and the optical part for dark field observation;
a second slider having the optical part for dark field observation and disposed on the microscope body of the microscope movably in the direction parallel with movement and return of the glare-proof optical part and the optical part for dark field observation; and
a positioning mechanism for positioning the first and second sliders in a position where the glare-proof optical part and the optical part for dark field observation are moved onto the optical path and a position where they are returned from the optical path.
According to such a structure, the glare-proof optical part and the optical part for dark field observation are held in the first and second sliders provided movably in the direction parallel with the directions of the movement and return of the optical parts. Therefore, the moving and returning operations can be carried out smoothly. In addition, there is provided the positioning mechanism for positioning the sliders in the position where the glare-proof optical part and the optical part for dark field observation are moved onto the optical path and the position where they are returned from the optical path. Therefore, it is possible to accurately position the glare-proof optical part and the optical part for dark field observation on the optical path.
Further, in the bright and dark field switching device, it is preferable that the switching mechanism includes:
a sleeve disposed on the microscope body slidably in the direction in parallel with the direction of the movement and return of the glare-proof optical part and the optical part for dark field observation and having a first operation portion on an outer end thereof;
a shaft provided slidably in the sleeve and having a second operation portion on an outer end thereof;
a first coupling member for coupling the sleeve to the first slider; and
a second coupling member for coupling the shaft to the second slider,
wherein when one of the first operation portion and the second operation portion is slid in one direction, the other of the first operation portion and the second operation portion is engaged and slid with the one of the first operation portion and the second operation portion, and the first operation portion is disengaged from the second operation portion when the first operation portion is slid in the other direction.
According to such a structure, for instance, if the first operation portion (sleeve) is slid in one direction (for example, a pull-out direction) in a state in which the optical part for dark field observation is positioned on the optical path, the second operation portion (shaft) is also slid together in one direction because the second operation portion is engaged with the first operation portion. Consequently, the optical part for dark field observation is returned from the optical path and the glare-proof optical part is positioned on the optical path.
Subsequently, when the first operation portion (sleeve) is slid in the other direction (for example, a push-in direction), the first operation portion is disengaged from the second operation portion. Therefore, the second operation portion (shaft) is not slid but only the first operation portion (sleeve) is slid in the other direction. Consequently, the glare-proof optical part is returned from the optical path. Therefore, the state in which any optical part is not positioned on the optical path is obtained, that is, switching into bright field observation is carried out.
Then, when the second operation portion (shaft) is slid in the other direction, the optical part for dark field observation is positioned on the optical path, that is, switching into dark field observation is carried out.
Accordingly, when the first and second operation portions positioned coaxially are simply slid, the switching can be carried out from the bright field observation to the dark field observation. Also in that case, the glare-proof optical part is once positioned on the optical path before the bright field observation is changed from the dark field observation. Therefore, the switching operation can be carried out without dazzling the observer.
In the bright and dark field switching device, it is preferable that the first operation portion includes a concave portion on an outer end face thereof, and the second operation portion includes a flange portion having such a size as to be almost accommodated in the concave portion, wherein the flange portion of the second operation portion is accommodated in the concave portion of the first operation portion and the second operation portion is engaged and slid with the first operation portion when the first operation portion is slid in one direction.
According to such a structure, the concave portion is provided on the outer end face of the first operation portion and the flange portion is provided on the second operation portion. Therefore, the engagement and disengagement of the first and second operation portions can be implemented with a very simple and inexpensive structure.
The above-mentioned the bright and dark field switching device may further comprises:
an optical part for bright field observation disposed on the second slider to be positioned on the optical path when the optical part for dark field observation is returned from the optical path.
The optical part for bright field observation indicates a condenser lens for a bright field and a filter for a bright field.
With such a structure, the optical part for bright field observation is attached to the second slider. By positioning the second slider on the optical path, therefore, the bright field observation can be carried out through the optical part for bright field observation.
A microscope for observing an object to be measured, according to the present invention, comprises:
a body for mounting the object to be measured thereon;
an illuminating optical system for illuminating the light to the object to be measured mounted on the body;
an observing optical system for observing the light transmitted form the object to be measured;
a glare-proof optical part for limiting the amount of light illuminated form the illuminating optical system;
an optical part for dark field observation;
a guide mechanism for holding the glare-proof optical part and the optical part for dark field observation such that they can be moved to the optical path and can be returned from the optical path; and
a switching mechanism for moving the glare-proof optical part and the optical part for dark field observation to the optical path and returning them from the optical path, and for moving the glare-proof optical part together and positioning the glare-proof optical part on the optical path only when returning the optical part for dark field observation from the optical path,
wherein the glare-proof optical part and the optical part for dark field observation are provided on both sides with the optical path of the illuminating optical system interposed therebetween.